JP2006064979A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which forms an image using toner in which wax for improving the releasing property is packed and which reduces uneven glossiness in the image to thereby provide the good image of high glossiness. <P>SOLUTION: The toner containing resin binder, color material and the wax for improving the releasing property is used. The toner image formed by using the toner is transferred on a recording sheet, thereafter, fixed by heating and pressurizing the recording sheet in the fixing apparatus 15. Thereafter, the recording sheet is guided to a both-side transport path 18 which is used for both-side image formation, then, the sheet is turned upside down, and guided to the fixing apparatus again. In this case, the temperature of a pressure roll 15b coming in contact with the toner image is set slightly higher than the melting point of the wax. The toner image comes in contact with the pressure roll, and the wax is melted again, then, the uneven glossiness generated after the recording sheet passes through the fixing apparatus before is eliminated. Thereafter, the temperature of the toner image becomes equal to or below the melting point before the toner image comes in contact with the transport roll 23, then, the occurrence of remarkable uneven glossiness due to the contact with the transport roll is suppressed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that forms a toner image by selectively attaching toner to a latent image due to a difference in electrostatic potential, transfers the toner image to a recording sheet, and then heats and pressurizes to form a fixed image. It is.

  An image forming apparatus using powdered toner can form a high-definition image and can output an image close to a photograph. In such a high-definition image, the demand for gloss is also high, and a high-gloss image is often required. For this reason, a so-called coated paper having a glossy coating layer formed on the surface is used as a recording sheet. After the toner image is transferred to the recording sheet, the toner image is sufficiently heated by a fixing device to obtain a highly glossy toner image. Has been made to form.

  However, when a high-gloss image is formed in this way, a portion where the gloss is uneven, that is, uneven gloss is likely to occur, and the quality of the image may be deteriorated. A representative example of uneven gloss is a so-called roll mark. As shown in FIG. 3, the toner image on the recording sheet P heated and pressurized by the fixing device 101 is sandwiched between roller pairs 102 for conveying the recording sheet in a state where the toner image is not sufficiently cooled. This occurs when the peripheral surface of the roller contacts the toner image. Many of the roll marks 103 thus generated reduce gloss.

Techniques for reducing such roll marks are disclosed in, for example, Patent Document 1 and Patent Document 2.
The apparatus described in Patent Document 1 blows cooling air to the recording sheet that has passed through the fixing device, and lowers the temperature of the toner image until the recording sheet comes into contact with a conveyance roll provided on the downstream side of the fixing device. It is what.

Further, in the image forming apparatus described in Patent Document 2, leveling means is provided in the area where the toner is in a soft state on the downstream side of the fixing device so that the toner image is pressed against and smoothed. Yes. As a result, even if a roll mark is formed in contact with the paper discharge roll, the surface of the toner image is smoothed by the leveling means and then the roll mark is to be erased. In addition, a leveling means is provided upstream from the paper discharge roll to smooth the surface of the toner image, and contact with the paper discharge roll in a state of being cooled below the glass transition temperature of the toner, thereby generating a roll mark. It has also been proposed to prevent.
Japanese Patent Laid-Open No. 2003-21978 Japanese Patent Laid-Open No. 2003-195663

  In recent years, in order to realize a high gloss color image similar to a photograph or printing, it has been proposed to use a toner having a good melting property encapsulating wax. For example, a high-gloss image can be obtained by transferring such toner onto a coated paper and fixing it while slowing the fixing speed and sufficiently heating. Even in a state where the toner is in high temperature due to contact with the heating roll or the heating belt in the fixing device, the releasability from the heating roll or the like is secured by the wax.

  However, when a toner containing wax is used to improve the releasability as described above, remarkable gloss unevenness that does not occur when a conventional toner is used may occur. That is, as shown in FIG. 3, when the recording sheet heated and pressed by the fixing device and having the toner image fixed thereon comes into contact with the recording sheet conveyance roll before being sufficiently cooled, the contacted portion becomes highly glossy. This causes uneven gloss. This unevenness of gloss is different from a roll mark in which gloss is lowered in an image using normal toner as described in Patent Document 1, and is different from a roll mark in which gloss is lowered. It is easy to cause noticeable uneven gloss.

  It has been found that this uneven gloss does not occur if the conveyance roll or the like is not brought into contact until the toner image and the recording sheet are sufficiently cooled. When a recording sheet is used, the cooling rate is slow, and it may be difficult to sufficiently cool the sheet until it contacts the transport roll. Also, it is difficult to arrange an apparatus having a sufficient cooling function in a miniaturized image forming apparatus.

  The present invention has been made to solve the above-described problems, and its purpose is to reduce gloss unevenness of a toner image using a toner containing a wax for improving releasability, It is to obtain a good image with high gloss.

  In order to solve the above-mentioned problems, the invention according to claim 1 includes an image forming unit that forms a toner image by selectively attaching powdery toner to a latent image due to a difference in electrostatic potential, and the toner. Transfer means for transferring an image directly to a recording sheet or via an intermediate transfer member, and fixing for fixing the toner image transferred on the recording sheet by applying pressure and heating to the recording sheet The toner includes a resin binder, a color material, and a wax that improves releasability, and the toner image is fixed by passing through the fixing device. The recording sheet passes through the fixing device again, and when it passes for the second time, the temperature of the member in contact with the toner image is controlled to be higher than the melting point of the wax and lower than the fixing temperature of the toner image. Provide The

  It became clear in the process of completing the present invention that the wax contained in the toner was rapidly cooled from the melted state and the wax crystallized and became highly glossy when the temperature dropped below the melting point. The present invention has been made on the basis of this fact, and after the melted wax is slowly cooled to a temperature below the melting point, the toner image is melted in such a manner that a member for conveying a recording sheet comes into contact therewith. In the following, rapid cooling is avoided and only the contact portion is prevented from becoming highly glossy.

In the image forming apparatus, the toner image that first passes through the fixing device and is fixed on the recording sheet is rapidly cooled and becomes highly glossy when it comes into contact with a member such as a conveyance roll at a temperature equal to or higher than the melting point of the wax. Will occur. Wax generally has a lower melting point than the binder resin of the toner, and after passing through the fixing device, the temperature of the toner gradually decreases. However, a member such as a transport roll does not come into contact with the recording sheet until the temperature becomes lower than the melting point of the wax. Difficult to maintain.
When the toner image is guided again to the fixing device, the member in contact with the toner image is at a temperature higher than the melting point of the wax and lower than that at the time of fixing the toner image, and the wax is again melted and discharged from the fixing device. . However, since the temperature of the toner image is lower than that at the time of fixing, the temperature decreases in a short time and becomes below the melting point of the wax. After that, even if the wafer is brought into contact with a member such as a transport roll and rapidly cooled, the wax temperature is not higher than the melting point, so that the gloss is not remarkably high and the occurrence of uneven gloss is suppressed.

  According to a second aspect of the present invention, there is provided image forming means for selectively attaching powdery toner to a latent image due to a difference in electrostatic potential to form a toner image; and the toner image directly on a recording sheet or in the middle Transfer means for transferring to a recording sheet via a transfer member, a heating member that comes into contact with an unfixed toner image in a heated state, and a pressure member that presses the recording sheet carrying the toner image against the heating member. A fixing device that heats and pressurizes the toner image on the recording sheet passing between the heating member and the pressure member and fixes the toner image on the recording sheet. As the toner, a resin binder, a color material, And a double-sided conveyance path that guides the recording sheet that has passed through the fixing device to the transfer position of the toner image and the fixing device by reversing the recording sheet that has passed through the fixing device. With When passing through the transfer position again through the double-sided conveyance path, the temperature of the pressure member that contacts the toner image when passing through the fixing device again without passing through the toner image is It is an object of the present invention to provide an image forming apparatus which is set to be equal to or higher than the melting point of the wax and lower than the temperature of the heating member.

  In this image forming apparatus, a recording sheet carrying an unfixed toner image is introduced between a heating member and a pressure member of the fixing device, and the toner image comes into contact with the heating member to be melted and pressed onto the recording sheet. Is done. The recording sheet discharged from the fixing device is conveyed while maintaining the high temperature of the toner image, and gloss unevenness occurs when it contacts a member such as a conveying roll. Thereafter, when the recording sheet passes through the transfer position again and is guided to the fixing device, the front and back are reversed, and the toner image comes into contact with the pressure member that is in contact with the back surface of the recording sheet at the time of fixing. Since the pressure member is pressed against the back side of the recording sheet at the time of fixing, the temperature can generally be lower than that of the heating member. Therefore, when the recording sheet is again guided to the fixing device and the toner image comes into contact, it is easy to make the temperature of the pressure member higher than the melting point of the wax and lower than the heating temperature at the time of fixing the toner image. Then, the wax contained in the toner image is melted again by coming into contact with the pressure member maintained above the melting point, and the uneven gloss is eliminated. However, the temperature is lower than the temperature at which the toner image at the time of fixing is melted, and after it is discharged from the fixing device again, it quickly becomes below the melting point of the wax. Therefore, even if a member such as a transport roll subsequently contacts the toner image, the contacted portion does not become highly glossy and the occurrence of significant gloss unevenness can be suppressed.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the temperature of the pressure member is predetermined when the recording sheet that has passed through the fixing device passes through the fixing device again. It is assumed that the conveyance speed of the sheet conveyance member or the timing of feeding the recording sheet to the fixing device is adjusted so that the temperature becomes the following temperature.

  When the temperature of the pressure member when melting and fixing the toner image on the recording sheet is much higher than the melting point of the wax, an appropriate temperature higher than the melting point is required before the recording sheet is again introduced into the fixing device. It is desirable to reduce to In this image forming apparatus, it is possible to adjust the sheet conveyance speed or the timing for re-feeding the recording sheet to the fixing device in the double-sided conveyance path that conveys the recording sheet once passed through the fixing device. Accordingly, the recording sheet can be introduced into the fixing device at the timing when the heating member is stopped and the temperature of the heating member and the pressure member is lowered to an appropriate temperature. Accordingly, the toner image on the recording sheet discharged again from the fixing device is quickly cooled below the melting point of the wax, and the occurrence of uneven glossiness can be suppressed even if the toner image comes into contact with the conveyance roll or the like thereafter.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the second aspect, the fixing device can change a pressure contact force between the heating member and the pressure member, and the recording sheet It is assumed that the pressure contact force when the toner passes again through the fixing device is set to be smaller than the pressure contact force when first passing and fixing the toner image.

  The recording sheet on which the toner image has been fixed once passing through the fixing device does not need to be pressurized with a large pressure when the toner image is again introduced into the fixing device. In other words, it is sufficient if the gloss unevenness can be eliminated by contacting the pressure member, and a smaller pressure is sufficient when the molten toner image is pressure-bonded. Then, when the recording sheet passes through the fixing device again, the pressure contact force between the heating member and the pressure member is set to be smaller than that at the time of fixing the toner image, so that the heating roll driven by sandwiching the recording sheet or The driving force of the pressure roll can be reduced. Therefore, the power load and energy consumption can be reduced.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the high-quality mode in which the recording sheet that has passed through the fixing device is reintroduced into the fixing device; It is assumed that there is provided a mode switching means for switching to the standard mode in which the recording sheet on which the toner image is fixed after passing through the fixing device is discharged as it is.

  The image forming apparatus according to the present invention adds a step of introducing the recording sheet once discharged through the fixing device into the fixing device again, and this can provide high image quality with less gloss unevenness. Efficiency is reduced. As described above, when the process of guiding the recording sheet to the fixing device is performed again, the high image quality mode can be switched to the normal mode in which such a process is not performed. Efficiency can be improved.

  As described above, in the image forming apparatus according to the present invention, the recording sheet after passing through the fixing device can be reintroduced into the fixing device, and gloss unevenness can be eliminated at a temperature lower than the temperature at the time of fixing. When the toner image is discharged again from the fixing device, the temperature of the toner image is lower than that at the time of fixing the toner image. be able to. Therefore, even if a member such as a transport roll comes into contact, this portion does not become highly glossy, and the occurrence of significant gloss unevenness can be suppressed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an image forming apparatus which is an embodiment of the invention described in claim 1 or claim 2.
The image forming apparatus includes four image forming units 10a, 10b, 10c, and 10d that form yellow, magenta, cyan, and black toner images, and is endless so as to face each of these image forming units 10. A belt-like intermediate transfer member 11 is supported, and the peripheral surface is driven to rotate. A transfer roll 12 is disposed on the downstream side of the position where the image forming unit faces the intermediate transfer body 11 so as to face the intermediate transfer body 11. After that, the recording sheet is sent. A fixing device 15 that heats and pressurizes the toner image to press the toner image onto the recording sheet is provided downstream of the secondary transfer portion in the recording sheet conveyance path, and the toner image is fixed further downstream. A paper discharge tray 16 for storing the recorded sheet is provided. In addition, a gate 17 is provided in the conveyance path from the fixing device 12 to the paper discharge tray 16, and a double-side conveyance path 18 that reverses the front and back of the recording sheet and conveys the recording sheet upstream to the position where the transfer roll 12 is provided. ing.
On the other hand, on the downstream side of the secondary transfer portion in the circumferential direction of the intermediate transfer body 11, the intermediate transfer is performed in order to collect the toner remaining without being transferred to the recording sheet in the secondary transfer portion and the patches that are not secondary transferred. A cleaning device 19 is provided facing the body 11.

  Each of the image forming units 10a, 10b, 10c, and 10d has a photosensitive drum 1 (image carrier) on which an electrostatic latent image is formed, and around each photosensitive drum 1, A charging device 2 that charges the surface of the photosensitive drum substantially uniformly, a developing device 3 that selectively transfers toner to a latent image formed on the photosensitive drum, and forms a toner image, and a photosensitive drum 1 A transfer device 4 that primarily transfers the upper toner image onto the intermediate transfer member 11 and a cleaning device 5 that recovers the toner remaining on the photosensitive drum 1 after the transfer are provided. An exposure device 6 for writing an electrostatic latent image by irradiating each uniformly charged photosensitive drum 1 with image light based on an image signal is provided.

  The charging device 2 includes a roll-shaped member obtained by coating a stainless steel cylindrical cored bar with a medium-resistance rubber. The charging device 2 applies a voltage obtained by superimposing an AC voltage on a DC voltage to apply the surface of the photosensitive drum 1. It is charged to a desired voltage. The DC component Vh of the voltage applied to the charging device 2 is −600 [V], and the superimposed AC peak-to-peak value Vbpp is 1400 [V].

  The exposure device 6 generates a flashing laser beam based on an image signal, and scans this in the main scanning direction (axial direction) of each photosensitive drum 1 by a polygon mirror. As a result, electrostatic latent images corresponding to the images of the respective colors are formed on the surfaces of the respective photosensitive drums 1.

The developing device 4 uses a two-component developer containing toner and a magnetic carrier as a developer, and is magnetically attracted to the developing roll and conveyed. Then, a layer having an appropriate thickness is formed on the developing roll by a regulating blade and supplied to a position facing the photosensitive drum 1. A developing bias voltage Vd = −500 [V] is applied to the developing roll in order to transfer the toner to the electrostatic latent image on the photosensitive drum 1.
The toner is charged negatively mainly by friction with a magnetic carrier, and contains a coloring material, a binder resin, and paraffin wax. The melting point of the binder resin is about 250 ° C., the glass transition temperature is about 100 ° C., and the melting point of the paraffin wax is about 90 ° C.

  The photosensitive drum 1 is obtained by forming an organic photoreceptor layer on the peripheral surface of a cylindrical member made of metal, and −200 [V] is applied as a bias voltage Vl to the metal portion.

The intermediate transfer body 11 disposed so as to face the image forming units 10a, 10b, 10c, and 10d is made of a resin film having a thickness of about 10 to 300 μm, and a polyimide film or the like is used. In addition, when the toner image is electrostatically transferred from the photosensitive drum 1 to the intermediate transfer member 11, a powder of a conductive material such as carbon black is mixed in the resin film so as not to disturb the image. The volume resistivity is adjusted to about 10 ¹⁰ Ωcm.

  A driving roll 21 and a counter roll 22 are arranged inside the intermediate transfer body 11, and the intermediate transfer body 11 is stretched around these and moves around in the direction of arrow A shown in the drawing. Yes.

  The transfer roll 12 is provided at a position facing the opposing roll 22 and is pressed against the opposing roll 22 via the intermediate transfer body 11. The transfer roll 12 is a roll formed by forming an outer peripheral portion of a metal core material with a conductive rubber material, and a bias voltage for transfer is applied between the opposite roll 22. .

  As shown in FIG. 2, the fixing device 15 includes a heating roll 15a having a built-in heating source and a pressure roll 15b pressed against the heating roll 15a. These are arranged in parallel and pressed against each other. The nip portion to be formed is formed. The recording sheet to which the toner image has been transferred is sent to the nip portion, heated and pressed between the heated roll 15a and the pressure roll 15b that are driven to rotate, and the melted toner is pressed onto the recording sheet. It is supposed to be.

  The heating roll 15a is formed by forming an elastic body layer such as a heat-resistant rubber on the peripheral surface of a metal core, and forming a release layer on the surface thereof. A halogen heater is incorporated as a heating source. ing. The pressure roll 15b is obtained by coating a metal cored bar with a surface release layer.

  In the downstream conveyance path of the fixing device 15, a recording sheet conveyance roll 23 and a paper discharge roll 24 that sends the recording sheet to the paper discharge tray 16 are provided. In between, a gate 17 for switching the conveyance direction of the recording sheet is provided. The gate 17 is switched when the trailing edge of the recording sheet reaches the paper discharge roll 24, and reverses the conveying direction to feed the recording sheet into the double-sided conveying path 18.

The double-sided conveyance path 18 conveys the recording sheet having the toner image fixed on one side to the upstream side of the transfer position when the toner image is formed on both sides. , The surface facing the intermediate transfer member 11 is inverted, and the toner image can be transferred to the back surface of the surface to which the toner image has been transferred first.
Further, even when the toner image is transferred to only one side, the double-sided conveying path 18 is selected when the high image quality mode is selected and the gloss unevenness of the image surface is to be eliminated. Used to transport the sheet to the upstream side of the transfer position. At this time, the conveyed recording sheet abuts against the registration roll 25 and is temporarily stopped. When the temperature of the pressure roll detected by the temperature sensor 26 reaches a predetermined value, the conveyance of the recording sheet is resumed. It has become.

Next, the operation of the image forming apparatus will be described.
Yellow, magenta, cyan, and black toner images are formed by the four image forming units 10a, 10b, 10c, and 10d provided to face the intermediate transfer member 11, respectively. The toner image is formed by the following process.
Each of the photosensitive drums 1 is charged almost uniformly by the charging device 2, and a laser beam that is turned on / off according to an image signal is emitted from the exposure device 6. As a result, the charge at the position irradiated with light is attenuated, and a latent image is formed on the photosensitive drum 1 due to the difference in electrostatic potential. The electrostatic latent image on each photosensitive drum 1 is developed by toner transfer at a position facing the developing device 3, and a toner image is formed on the photosensitive drum 1.

  The formed color toner images are transferred onto the intermediate transfer body 11 in a superimposed manner by the transfer device 4. As a result, a color image in which a plurality of color toner images are superimposed on the intermediate transfer body 11 is formed. The toner images of a plurality of colors formed on the intermediate transfer body 11 are transferred onto the recording sheet conveyed from the sheet tray 13 at a position where the intermediate transfer body 11 faces the transfer roll 12 and sent to the fixing device 15. . The heating roll 15a of the fixing device is heated to a temperature sufficient to melt the toner image. A recording sheet is sandwiched between the heating roll 15a and the pressure roll 15b, and the toner image is melted and recorded. Crimped onto the sheet.

  The recording sheet that has passed through the fixing device 15 is sandwiched and conveyed by the downstream conveyance roll 23. A plurality of rolls having a predetermined width are arranged in the width direction of the recording sheet, and the conveyance roll 23 has a toner image rapidly cooled at a portion in contact with the conveyance roll 23, resulting in high gloss and uneven gloss. Thereafter, when the rear end of the recording sheet reaches the paper discharge roll 24, the conveyance direction is reversed. At this time, the gate 17 is switched, and the recording sheet is fed into the duplex conveying path 18. Then, it is abutted against a resist roll 25 provided on the upstream side of the transfer position and temporarily stopped.

On the other hand, in the fixing device 15, the energization to the halogen lamp 15c built in the heating roll 15a is stopped after the recording sheet passes, and the temperatures of the surfaces of the heating roll 15a and the pressure roll 15b gradually decrease. The pressure roll 15b does not have a built-in heating source and is lower in temperature than the heat roll 15a. However, the surface temperature of the pressure roll 15b decreases, and the temperature slightly higher than the melting point of the wax contained in the toner, for example, When the temperature sensor 26 detects that the temperature is about 10 ° higher than the melting point, the conveyance of the recording sheet that has been stopped by abutting against the resist roll 25 is resumed.
The recording sheet is not temporarily stopped by the resist roll 25, but the conveyance speed of the double-sided conveyance path 18 is adjusted, and the recording sheet is fixed when the surface temperature of the pressure roll 15b reaches a predetermined temperature. You may control to reach 15.

  The recording sheet that has been transported passes through a position where the transfer roll 12 faces the intermediate transfer body 11, but at this time, the toner image is not transferred. Then, the toner image is fed into the fixing device 15 and the toner image comes into contact with the pressure roll 15b. Since the pressure roll 15b is maintained at a temperature higher than the melting point of the wax, it melts the wax and eliminates the uneven gloss caused in the previous step.

  The recording sheet sent out from the fixing device 15 is heated again in contact with the pressure roll 15b and the heating roll 15a, but the temperature is only slightly higher than the melting point of the wax. The temperature drops to 23, and when reaching the transport roll, the temperature is lower than the melting point of the wax. For this reason, even when the toner image is brought into contact with the conveying roll 23 and rapidly cooled, the toner image does not become highly glossy and the occurrence of gloss unevenness can be suppressed. Then, the paper is discharged to the paper discharge tray 16 through the paper discharge roll 24.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic sectional view of a fixing device used in the image forming apparatus shown in FIG. 1 and a transport roll provided downstream thereof. FIG. 6 is a schematic perspective view for explaining problems in a conventional image forming apparatus, and shows a fixing device, a transport roll provided on the downstream side, and a roll mark generated on a recording sheet.

Explanation of symbols

1: Photosensitive drum, 2: Charging device, 3: Developing device, 4: Transfer device, 5: Cleaning device, 6: Exposure device, 10: Image forming unit, 11: Intermediate transfer member, 12: Transfer roll, 13: Sheet tray, 14: conveyance path, 15: fixing device, 16: paper discharge tray, 17: gate, 18: double-sided conveyance path, 19: cleaning device, 21: driving roll, 22: opposite roll, 23: conveyance roll, 24 : Paper discharge roll, 25: Registration roll, 26: Temperature sensor

Claims (5)

Image forming means for selectively attaching powdery toner to a latent image due to a difference in electrostatic potential to form a toner image;
Transfer means for transferring the toner image directly to the recording sheet or to the recording sheet via an intermediate transfer member;
An image forming apparatus comprising: a fixing device that pressurizes and heats the toner image transferred onto the recording sheet and fixes the toner image on the recording sheet;
The toner includes a resin binder, a coloring material, and a wax that improves releasability,
The recording sheet on which the toner image has been fixed after passing through the fixing device passes through the fixing device again, and at the second pass, the temperature of the member in contact with the toner image is equal to or higher than the melting point of the wax, and the toner image An image forming apparatus controlled to a temperature lower than the fixing temperature of the image forming apparatus. Image forming means for selectively attaching powdery toner to a latent image due to a difference in electrostatic potential to form a toner image;
Transfer means for transferring the toner image directly to the recording sheet or to the recording sheet via an intermediate transfer member;
A heating member that contacts an unfixed toner image in a heated state and a pressure member that presses a recording sheet carrying the toner image against the heating member, and passes between the heating member and the pressure member. A fixing device that heats and pressurizes the toner image on the recording sheet and fixes the toner image on the recording sheet;
An image forming apparatus using, as the toner, a resin binder, a color material, and a wax that improves releasability,
A recording sheet that has passed through the fixing device is provided with a double-sided conveyance path that reverses the front and back and guides the toner image to a transfer position and the fixing device.
When passing the transfer position again through the double-sided conveyance path, the temperature of the pressure member that contacts the toner image passes without transferring the toner image and passes through the fixing device again. An image forming apparatus, wherein the image forming apparatus is set to be equal to or higher than a melting point of the wax and lower than a temperature of the heating member.   The double-sided conveyance path is arranged such that when the recording sheet that has passed through the fixing device passes through the fixing device again, the pressure of the pressure member becomes a predetermined temperature or the conveying speed of the sheet conveying member or the fixing device. The image forming apparatus according to claim 2, wherein the timing for feeding the recording sheet is adjusted.   The fixing device can change the pressure contact force between the heating member and the pressure member, and the pressure contact force when the recording sheet passes through the fixing device again passes through the toner first. The image forming apparatus according to claim 2, wherein the image forming apparatus is set to be smaller than a pressing force when fixing an image. A mode switching means is provided between a high image quality mode in which the recording sheet after passing through the fixing device is reintroduced into the fixing device and a standard mode in which the recording sheet having the toner image fixed through the fixing device is discharged as it is. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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